Question 187668
find the length of the line segment between (2,-1) and (3,5). 
find the midpoint of the line segment between the points (2,-1) and (3,5)
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You can always make a right triangle by adding a 3rd point where a vertical line thru one point, and a horizontal line thru the other, intersect.
Then use Pythagoras.
{{{s = sqrt(dy^2 + dx^2)}}} where dy is the difference in y, dx in x.
{{{s = sqrt((5-(-1))^2 + (3-2)^2)}}}
{{{s = sqrt(36 + 1)}}}
distance = sqrt(37)
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To find the midpoint, take the average of x and y separately
xm = (2+3)/2 = 2.5
ym = (-1+5)/2 = 2
midpoint = (2.5,2)